Have you considered what it would cost to purchase a replacement part versus what you will spend to make your own part?
If you decide to make the part yourself, I'd recommend using the best alloy steel and the best heat treatment, since the added cost will not be significant. The cost for material (like Nitralloy N bar) will be less than $50, and heat treatment (quench, temper and nitride) will likely cost around $150-200. But rough machining and finish grinding may likely cost around $1000 or more.